1. Field of the Invention
This invention relates to integrated circuit packages, and more particularly is concerned with apparatus for attaching an aluminum heatsink to a ceramic integrated-circuit package.
2. Prior Art
One technique for attaching an aluminum heatsink to a ceramic integrated-circuit package is to use a silver-filled epoxy material for bonding a surface of the heatsink to a surface of the ceramic package. The silver-filled epoxy is first applied to the attachment surface of the ceramic integrated-circuit package. Then, a surface of the heatsink is placed over the attachment surface of the package in contact with the silver-filled epoxy. The epoxy is then cured for a certain amount of time in a heated oven to form a bond between the heatsink and the ceramic package. This technique has several disadvantages. The thermal conductivity of the silver-filled epoxy material is not as good as a direct metal connection between the heatsink and the ceramic package. Additional handling and processing time is required for transferring and curing the silver-filled epoxy material in an oven. The epoxy bond is subject to failure during, for example, a steam pressure pot test.
Another technique for attaching an aluminum heatsink to a ceramic integrated-circuit package is to use a threaded copper stud, which is attached to the ceramic package. The aluminum heatsink has internal threads into which the copper stud is threaded. The copper is soft and is deformed by the harder internal threads of the aluminum heatsink so a loose mechanical bond is formed between the copper stud and the heatsink.
Consequently, the need exists for an improved technique for attaching an aluminum heatsink to a ceramic integrated-circuit package which will provide strong and reliable metallic mechanical and thermal connections between the heatsink and the ceramic package, without requiring additional handling and processing time, such as required for connections made with epoxy material.